“Yā Sīn is the heart of the Qur'an — whoever recites it, Allah writes for him the reward of reciting the Qur'an ten times.”
Al-Albānī grades this narration mawḍūʿ (fabricated). Bashār ʿAwwād Maʿrūf and Zubair Ali Zai both grade it ḍaʿīf (weak). At-Tirmidhī himself calls it gharīb and notes its chain is known only through a single route.
Sūrat Yā Sīn is of course part of the Qur'an and reciting it is good. What is not established is this specific claim about its reward.
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